On July 21, 1969, Buzz Aldrin climbed gingerly out of Eagle, Apollo 11’s lunar module, and joined Neil Armstrong on the Sea of Tranquility. Looking up, he said, “Beautiful, beautiful, magnificent desolation.” They were alone; but their presence on the moon’s silent, gray surface was the culmination of a convulsive collective effort.

Eight years before, President John F. Kennedy had asked the United States Congress to “commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth.” His challenge disturbed the National Aeronautics and Space Administration’s original plan for a stepped, multi-generational strategy: Wernher von Braun, NASA’s chief of rocketry, had thought the agency would first send men into Earth’s orbit, then build a space station, then fly to the moon, then build a lunar colony. A century hence, perhaps, humans would travel to Mars. Kennedy’s goal was also absurdly ambitious. A few weeks before his speech, NASA had strapped an astronaut into a tiny capsule atop a converted military rocket and shot him into space on a ballistic trajectory, as if he were a circus clown; but no American had orbited the planet. The agency didn’t really know if what the president asked could be done in the time he allowed, but it accepted the call.